Andrew M Brown is the Telegraph's obituaries editor.

Charles Kennedy and his wife to separate: How does alcoholism affect marriages?

Charles Kennedy, the former Liberal Democrat leader, pictured with his wife (Photo: PA)

Sadly when we read this morning that Charles Kennedy is to separate from Sarah, his wife of eight years, it doesn't come as an earth-shattering surprise. Mr Kennedy has a well-documented history of alcohol problems and it is common for married alcoholics to separate – it's probably just as common after the drinker gets sober. Any addiction counsellor will testify that getting off the booze is one problem, then the next issue is what to do about the patient's steady relationship. I say clearly: we don't know the cause of Mr Kennedy's trouble, but it's an opportunity to say a few things about addiction and its effect on relationships and marriages.

Often – and I do not know that this is the case with Mr Kennedy and his wife – the relationship can be seen in the cold light of day as having a structure that one way or another supported the addiction. In the recovery business they use the term "co-dependency" to describe the role that is forced on the partner of the addict. She, and it is "she" typically (but of course it can be either sex), falls into the habit of caretaking. She may clean up after her partner, make excuses for him, ring his office to say he's not coming in, and generally cover up the hideous reality of advanced addiction. In this sense, although the partner is not herself addicted, she is sharing the addiction – co-dependent – and she's allowing it to keep it going. She's "enabling", to use the jargon.

If there are children, the caretaker will shoulder the entire responsibility not just of the basic childcare but also of the emotional involvement that children need. An addict is, basically, interested in the next drink/drug, and that's it. Ensuring a steady and ample supply is an all-consuming obsession. Children are an irritating distraction, a bore.

Where difficulties can arise after the alcoholic starts to recover is that all of a sudden the whole dynamic, the power balance, of the relationship or marriage has altered. The addict no longer needs round the clock caretaking. He can stand on his own two feet. The co-dependent partner experiences a loss, simply because she's no longer needed to play this massive supporting role in the partnership. What does she do now?

Of course, I'm simplifying the way things happen, but this co-dependency issue is real. Other things are going on too, naturally. For instance, while the crisis was carrying on, neither spouse/partner could think about what to do next. It was just a question of lurching from one near-miss to the next and avoiding catastrophe. Now the dust has settled, the addict is recovering, the couple may start to see the cracks in the plaster for the first time. And at last, they have the energy to do something about it, and that may mean curtains for the relationship. It's possible also that the relationship was contributing to the addiction directly – if, for example, it was an intolerable set-up where neither half could stand the other.

There is a happier outcome, as well. Go to any AA or NA meeting and you'll find men and women who are only there by the grace of God and because a strong partner said: "I've had enough." Those words, as long as they're backed up by concrete action – throwing the boozer out, for example – can be the best thing for the still-suffering addict to hear, a meaningful ultimatum that promises real consequences if the person refuses to address the problem. After that, many marriages can and do recover from the trials of addiction. Relationships that are based on love and promises of faithfulness "in sickness and in health" can emerge out of the tunnel of addiction into the light. They may feel battered, they may have to renegotiate aspects of the partnership, but, one day at a time, they'll be stronger for it.